Add GitHub interaction guidelines to CLAUDE.md (#10715)

Added explicit guidelines about GitHub interactions to ensure appropriate behavior when working with the xarray repository. These guidelines prevent unsolicited GitHub actions and require explicit user authorization for repository interactions.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <[email protected]>

Author: max-sixty

CLAUDE.md

@@ -19,3 +19,10 @@ uv run pytest xarray/tests/test_dataarray.py  # Specific file
 pre-commit run --all-files  # Includes ruff and other checks
 uv run dmypy run  # Type checking with mypy
 ```
+
+## GitHub Interaction Guidelines
+
+- **NEVER impersonate the user on GitHub** - Do not post comments, create issues, or interact with the xarray GitHub repository unless explicitly instructed
+- Never create GitHub issues or PRs unless explicitly requested by the user
+- Never post "update" messages, progress reports, or explanatory comments on GitHub issues/PRs unless specifically asked
+- Always require explicit user direction before creating pull requests or pushing to the xarray GitHub repository